Phorboxazole A (1) and B (2), originally isolated from the Indian ocean sponge Phorbas sp., display extraordinary biological properties, including high cell growth inhibitor activity against both fungal and human tumor cell lines. For example, in vitro bioassay of 1 and 2 against the National Cancer Institute's panel of 60 human tumor cell lines revealed a mean GI50 of 1.58×10−9M.

In April 2009, the isolation of hemi-phorboxazole A (3) was reported. Dalisay, D. S.; Molinski, T. F. Org. Lett. 2009, 11, 1967. Hemi-phorboxazole is the first example of a natural phorboxazole variant identified since phorboxazoles A and B were first reported in 1995 and is about 10,000 times less abundant than phorboxazoles A and B (cf. 0.07 vs. 500 ppm, respectively). The limited availability of the natural material precludes any significant evaluation of its biological activity. As such, methods for the preparation of (+) hemi-phorboxazole A are needed. Moreover, to explore and maximize the biological activity of (+) hemi-phorboxazole A, synthetic analogues are needed.
